1. Field of the Invention:
The invention relates generally to crop harvesting headers having "floating" cutterbars and more particularly to an improved drive system for such a cutterbar.
2. Description of the Prior Art:
U.S. Pat. No. 3,982,383 discloses a header having a floating cutterbar driven by a wobble drive mounted on the cutterbar. A spring-loaded idler pulley 112 maintains tension in the drive belt. The cutterbar is mounted on a plurality of parallel bar-type mechanisms 56. An example of maintaining belt tension throughout header movement is also shown in U.S. Pat. No. 2,459,379 wherein an idler pulley 54 is movable to maintain tension in the drive belt as the drive geometry changes.
In both of the above examples the idler pulley is spring-loaded and thus subject to a loading force which varies in accordance with variations in the spring force due to extension and retraction of the spring in operation. Moreover, in U.S. Pat. No. 3,982,383 the spring-loaded idler is moved in response to changes in the forces exerted on and by the drive belt. Since the drive belt itself is subject to variable loading, movement due to drive speed variations, stretching, and movement due to machine vibration and bouncing in field operation, it is ultimately an imprecise indicator of drive system changes.
A further problem associated with crop headers having reciprocating type cutterbars is accommodating loads imposed in the conversion of rotary to reciprocating movement. The problems become more complex where the cutterbar is of a floating type movable relative to the supporting header frame. In the prior art the wobble drive unit is mounted on and supported by the cutterbar with the result that lateral loads from the reciprocating knife are transferred to the wobble drive unit, to the cutterbar, and ultimately back to the header frame through the cutterbar mounting structure.